Thysanura
Encyclopedia
Thysanura is an order
of insect
s, encompassing silverfish
and firebrat
s, known for their three long caudal filaments.
The families Machilidae
and Meinertellidae
of the jumping bristletails were once included with Thysanura.
Occasionally, the correspondingly restricted order Thysanura is referred to as Zygentoma.
covering their bodies. Their movement is "fish-like" and makes it look as if they are swimming. They are less than 1 centimetre (0.393700787401575 in) long, and found in damp corners or amongst books and paper in houses.
Silverfish have flattened bodies and may be elongated or oval in shape. They have flexible antennae
and small or absent compound eyes. They have short mandibles
and relatively unspecialised mouthparts
. Many species also have a number of short appendages on their abdominal
segments, but the most distinctive feature of the group is the presence of three long, tail-like filaments extending from their last segment. The two lateral filaments are formed from the abdominal cerci
.
They may be found in moist, humid environments or dry conditions, both as free-living organisms or nest-associates.
Silverfish feed on cereals, paste, paper, starch in clothes, rayon
fabrics and dried meats. Silverfish can sometimes be found in bathtubs or sinks at night, as they have difficulty moving on smooth surfaces and so become trapped. Wild species often are found in habitats such as caves, and some are commensals living in association with ant
colonies, e.g., Trichatelura manni.
There are no current species formally considered to be at conservation risk, though several are troglobite
s limited to one or a few caves or cave systems, and these species run an exceptionally high risk of extinction.
and Tricholepidion gertschi from forests of northern California. Three species of Maindroniidae are found in the Middle East and in Chile. The Ateluridae (sometimes treated as a subfamily Atelurinae
within the Nicoletiidae) live in nests of ants and termites and are small and blind.
) beneath this thread and then coaxes a female to walk under the thread. When her cerci
contact the silk thread, she picks up the spermatophore with her genital opening. Sperm are released into her reproductive system, and then she ejects the empty spermatophore and eats it.
Silverfish continue to moult throughout their life, with several sexually mature instar
s, unlike more advanced insects. They are relatively slow growing, and lifespans of up to four years have been recorded.
Order (biology)
In scientific classification used in biology, the order is# a taxonomic rank used in the classification of organisms. Other well-known ranks are life, domain, kingdom, phylum, class, family, genus, and species, with order fitting in between class and family...
of insect
Insect
Insects are a class of living creatures within the arthropods that have a chitinous exoskeleton, a three-part body , three pairs of jointed legs, compound eyes, and two antennae...
s, encompassing silverfish
Silverfish
Lepisma saccharina, frequently called silverfish, fishmoths, carpet sharks or paramites, are small, wingless insects in the order Thysanura...
and firebrat
Firebrat
The Firebrat is a small insect similar to the Silverfish, both in the order Thysanura....
s, known for their three long caudal filaments.
The families Machilidae
Machilidae
Machilidae is a family of primitive insects belonging to the order Archaeognatha . There are around 250 described species worldwide. These insects are wingless, elongated and more or less cylindrical with a distinctive humped thorax and covered with tiny, close-fitting scales. The colour is usually...
and Meinertellidae
Meinertellidae
Meinertellidae is a small family of basal insects belonging to the order Archaeognatha. They are sometimes known as rock bristletails. These insects can be distinguished from members of the other Archaeognatha family, Machilidae, by the lack of scales at the base of the legs and...
of the jumping bristletails were once included with Thysanura.
Occasionally, the correspondingly restricted order Thysanura is referred to as Zygentoma.
Etymology
The name Thysanura is derived from the Greek θυσάνος, thysanos for fringe, tassel, bristle and ουρα, oura for tail, a reference to the three fanned out caudal filaments.Description and ecology
Silverfish are so called due to the silvery glitter of the scalesScale (zoology)
In most biological nomenclature, a scale is a small rigid plate that grows out of an animal's skin to provide protection. In lepidopteran species, scales are plates on the surface of the insect wing, and provide coloration...
covering their bodies. Their movement is "fish-like" and makes it look as if they are swimming. They are less than 1 centimetre (0.393700787401575 in) long, and found in damp corners or amongst books and paper in houses.
Silverfish have flattened bodies and may be elongated or oval in shape. They have flexible antennae
Antenna (biology)
Antennae in biology have historically been paired appendages used for sensing in arthropods. More recently, the term has also been applied to cilium structures present in most cell types of eukaryotes....
and small or absent compound eyes. They have short mandibles
Mandible (arthropod)
thumb|250px|The mandibles of a [[Bull ant]]The mandible of an arthropod is either of a pair of mouthparts used for biting, cutting and holding food. Mandibles are often simply referred to as jaws. Mandibles are present in the extant subphyla Myriapoda , Crustacea and Hexapoda...
and relatively unspecialised mouthparts
Insect mouthparts
Insects exhibit a range of mouthparts, adapted to particular modes of feeding. The earliest insects had chewing mouthparts...
. Many species also have a number of short appendages on their abdominal
Abdomen
In vertebrates such as mammals the abdomen constitutes the part of the body between the thorax and pelvis. The region enclosed by the abdomen is termed the abdominal cavity...
segments, but the most distinctive feature of the group is the presence of three long, tail-like filaments extending from their last segment. The two lateral filaments are formed from the abdominal cerci
Cercus
Cerci are paired appendages on the rear-most segments of many arthropods, including insects and arachnids but not crustaceans. Cerci often serve as sensory organs, but they may also be used as weapons or copulation aids, or they may simply be vestigial structures.Typical cerci may appear to be...
.
They may be found in moist, humid environments or dry conditions, both as free-living organisms or nest-associates.
Silverfish feed on cereals, paste, paper, starch in clothes, rayon
Rayon
Rayon is a manufactured regenerated cellulose fiber. Because it is produced from naturally occurring polymers, it is neither a truly synthetic fiber nor a natural fiber; it is a semi-synthetic or artificial fiber. Rayon is known by the names viscose rayon and art silk in the textile industry...
fabrics and dried meats. Silverfish can sometimes be found in bathtubs or sinks at night, as they have difficulty moving on smooth surfaces and so become trapped. Wild species often are found in habitats such as caves, and some are commensals living in association with ant
Ant
Ants are social insects of the family Formicidae and, along with the related wasps and bees, belong to the order Hymenoptera. Ants evolved from wasp-like ancestors in the mid-Cretaceous period between 110 and 130 million years ago and diversified after the rise of flowering plants. More than...
colonies, e.g., Trichatelura manni.
There are no current species formally considered to be at conservation risk, though several are troglobite
Troglobite
Troglobites are small cave-dwelling animals that have adapted to their dark surroundings. Troglobite species include spiders, insects, fish and others. They live permanently underground and cannot survive outside the cave environment. Troglobite adaptations and characteristics include a heightened...
s limited to one or a few caves or cave systems, and these species run an exceptionally high risk of extinction.
Families
Lepismatidae is the largest family, widespread with more than 200 species, many living in human habitations. The Nicoletiidae are small and live in soil litter, humus and under stones. The Lepidothrichidae are represented by two species Lepidothrix pilifera from Baltic amberBaltic amber
The Baltic region is home to the largest known deposit of amber, called Baltic amber or succinite, with about 80% of the world's known amber found there. It dates from 44 million years ago...
and Tricholepidion gertschi from forests of northern California. Three species of Maindroniidae are found in the Middle East and in Chile. The Ateluridae (sometimes treated as a subfamily Atelurinae
Atelurinae
Atelurinae is a subfamily of primitive insects belonging to the order Thysanura. They are sometimes treated as a family Ateluridae. These are tiny and usually found within the nests of termites and ants with which they associate....
within the Nicoletiidae) live in nests of ants and termites and are small and blind.
Reproduction
Silverfish have an elaborate courtship ritual to ensure exchange of sperm. The male spins a silken thread between the substrate and a vertical object. He deposits a sperm packet (spermatophoreSpermatophore
A spermatophore or sperm ampulla is a capsule or mass created by males of various animal species, containing spermatozoa and transferred in entirety to the female's ovipore during copulation...
) beneath this thread and then coaxes a female to walk under the thread. When her cerci
Cercus
Cerci are paired appendages on the rear-most segments of many arthropods, including insects and arachnids but not crustaceans. Cerci often serve as sensory organs, but they may also be used as weapons or copulation aids, or they may simply be vestigial structures.Typical cerci may appear to be...
contact the silk thread, she picks up the spermatophore with her genital opening. Sperm are released into her reproductive system, and then she ejects the empty spermatophore and eats it.
Silverfish continue to moult throughout their life, with several sexually mature instar
Instar
An instar is a developmental stage of arthropods, such as insects, between each molt , until sexual maturity is reached. Arthropods must shed the exoskeleton in order to grow or assume a new form. Differences between instars can often be seen in altered body proportions, colors, patterns, or...
s, unlike more advanced insects. They are relatively slow growing, and lifespans of up to four years have been recorded.
External links
- Thysanura – Tree of Life Web Project
- Virginia Extension Service Article
- Harvard University Fact Sheet on silverfish and firebrats